The FLUORESCENCE/ISOLATED MUSCLE will make available to investigators a suite of photometry, high resolution fluorescence imaging, and isolated cardiac muscle equipment and the expertise to facilitate the proposed experiments. We will leverage existing microscopy facilities that are shared with the wider Johns Hopkins research community, as well as establish stations for the measurement of cardiac trabecula force and fluorescence simultaneously, to be shared exclusively with investigators. Fluorescence imaging of intact cells and tissues will be carried out utilizing the Johns Hopkins Multiphoton microscope facility, which is also directed. In addition to making the equipment available, a key support feature will be to train and assist investigators in the delicate procedure of muscle isolation and dye injection. For the intact muscle preparation, a well-trained technician will assist in the experiments, in consultation with a faculty investigator who has studied muscle performance in trabeculae from post-ischemic hearts and who has many years of experience in the technique.